Cathode-ray tube



Feb. 21, 1967 R. M. NORDBY INVENTOR. @0962 7??. WQWCZQ United StatesPatent O 3,305,123 CATHODE-RAY TUBE Roger M. N ordby, Wilmette, Ill.,assigner to Zenith Radio Corporation, Chicago, Ill., a corporation ofDelaware Filed Jan. 9, 1964, Ser. No. 336,732 9 Claims. (Cl. 220-2.1)

This invention relates in general to cathode-ray tubes and in particularto an improved cathode-ray tube and safety plate assembly for atelevision receiver.

The use of a highly evacuated cathode-ray tube in home entertainmentapparatus, such as a television receiver, necessitates precautionarymeasures in order to protect the viewer in the event of a tubeimplosion. Ofne such measure takes the form of a transparent safetyplate which is positioned directly in front of the display screen of thepicture tube. While a variety of arrangements for mounting this platehave been utilized, a common practice is to employ a support whichrigidly fixes the safety plate with respect to the tube as byperipherally anchoring the plate adjacent an opening in the front wallof the cabinet. As -will Ibe shown, this practice can contribute tosafety plate failure should the tube implode.

A tube implosion is generally initiated by a crack or a fault on thesurface of the tube envelope. Instantly, since substantial portions ofthe envelope surface are under tension due to the force exerted byatmospheric pressure, a multitude of additional fissures are developed.As a result, there is more or less a complete mechanical breakdown ofthe tube which is manifested, in part, by a violent dispersion of glassparticles. It is, of course, the purpose of the safety plate tointercept the flying glass and confine the eects of the implosion to thetelevision cabinet proper.

An additional factor to be considered is the effect of the implosionupon the safety plate itself particularly when the safety plate ishermetically sealed to the face plate of the tube as is required toeffect a dust seal therebetween. While being scored and scratched byiiying glass, the plate is simultaneously subjected to a substantialpressure differential, that is, a very low pressure on the inside andatmospheric pressure on the outside. As a result, the plate is driventoward the tube under the impetus f atmospheric pressure. When the edgeof the safety plate is rigidly constrained about its periphery, aspracticed in a common prior art arrangement, the plate tends to bowsubjecting the inner surface of the plate to tension forces. At thisparticular instant the plate is readily susceptible to failure becauseof the inability of the scratched inner surface to withstand the tensionforces. This problem has vbeen resolved in the past by resorting to theuse of a tempered or heavy glass plate, both rather expensiveexpedients.

An improvement in the method of mounting the safety plate is describedin Patent 3,084,217 which issued to Joseph P. Fiore et al. and isassigned to the same assignee as the present invention. This patentdescribes a mounting arrangement in which the safety plate is yieldablysuspended between the face plate of the tube and the cabinet or theescutcheon by a pneumatic mount. This mount comprises a gasket having achannel that embraces the plate about its perimeter and a bulbousportion that confronts the display panel to define with the channelportion a yieldable cushion which accommodates displacement of thesafety window upon occurrence of a tube implosion.

An alternative implosion precaution is to bond a safety window directlyto the face of the picture tube. In such an arrangement a safety window,having a bowl portion conforming substantially to the display panel ofthe tube and containing a quantity of transparent epoxy resin which dlPatented Feb. 21, 1967 fice covers the entire face of the tube, islaminated directly to the face of the tube envelope. As would beexpected, the additional processing and material required in making afully laminated tube is reflected in its cost which is substantialy morethan that of the picture tube arrangement herein considered.

It is therefore a general object of the invention to provide an improvedcathode-ray tube and safety plate arrangement.

It is a particular object of the invention to provide a unitarycathode-ray tube and safety plate assembly.

It is also an object of the invention to provide an improved method forbonding a safety plate to the face plate of a cathode-ray tube.

It is a further object of the invention to provide a cathode-ray tubearrangement which affords substantial economies over prior art safetyplate mounting arrangements.

A cathode-ray tube constructed in accordance with the inventioncomprises an envelope having a curved screen-bearing face plate with apredetermined viewing area and a safety plate with a transparent sectionhaving overall dimensions greater than those of the viewing area and acurvature conforming substantially to the curvature of the face plate.The safety plate is secured in an overlying spaced relation to the faceplate and hermetically sealed thereto by bonding means consisting of acontinuous layer of adhesive paste in intimate contact with and confinedto confronting portions of the envelope and the safety plate which areoutside of the face plate viewing area. The adhesive paste is cured soas to constitute a resilient gasket capable of yieldably accommodating4displacement of the safety plate relative to the face plate of thetube.

The features of this invention which are `believed to 'be novel are setforth with particularity in the appended claims. The invention, togetherwith further objects and advantages thereof, may best be understood,however, by reference to the following description taken in conjunctionwith the accompanying drawings, in the several figures of which likereference numerals identify like elements, and in which:

FIGURE 1 is a perspective view of a cathode-rayl tube embodying theinvention;

FIGURE 2 is a sectional view taken along lines 2 2 of FIGURE 1;

FIGURE 3 is a perspective view of apparatus employed in practicing theinvention;

FIGURE 3a is a fragmentary detail of FIGURE 3 illustrating the`deposition of a gasket forming sealant on the faceplate of acathode-ray tube;

FIGURE 4 is a perspective view of apparatus employed in practicing analternate embodiment of the invention;

FIGUR-E 4a is a fragmentary detail of FIGURE 4 illustrating thedeposition of a gasket forming sealant in accordance with an alternateembodiment of the invention; and

FIGURE 5 is a sectional view of a cathode-ray tube employing a safetywindow construction in accordance with an alternate embodiment of theinvention.

FIGURES 1 and 2 show a cathode-ray tube 10 comprising an envelope havinga neck 11, a funnel portion 12 and a curved faceplate 13 with `a -crown14 which is butt-sealed to the rim of funnel 12. A phosphor screen 15,which is deposited on the inside surface of faceplate 13, coverssubstantially all the inner surface thereof. The usable viewing area,however, is restricted to that portion which is bounded by the`dotted-line enclosure identified by reference numeral 16.

A safety plate or window 17 is disposed in an overlying relation tofaceplate 13 and has a transparent section essaies with overalldimensions greater than those of viewing area 16 and a curvatureconforming substantially to the curva- ,ture of faceplate 13. Safetyplate 17 is bonded to faceplate 13 and hermetically sealed thereto by aresilient gasket 18 which is in intimate adhesive contact with theconfronting peripheral portions of faceplate 13 and safety plate 17outside viewing area 16.

Gasket 18 not only bonds safety window 17 to faceplate 13, but, becauseof its resiliency, also accommodates displacement of safety plate 17relative to faceplate 13 as would be required in the event of tubeimplosion. Moreover, .as a hermetic seal, gasket 1S also serves toprevent dust, moisture and other contaminants from collecting on theviewing surface of the faceplate. Preferably, gasket 18 is compounded ofa viscous synthetic rubber base to which a solidifying or curing agenthas rbeen added. In an embodiment of the invention which was 'actuallyconstructed, a 'eyw'inch safety plate was bonded to a 19 inchcathode-ray ltube by a gasket formulated from a polysulfide polymerwhich was cured by the addition of a lead peroxide. Chemically, thepolysulfide polymers are methanes containing disulfide linkages. Thepolymer segments `are terminated with reactive mercaptan (SH). Theaverage structure -of a polysullide polymer may be represented asfollows although some of the polymers are segmented branched:

It is appreciated that the viscosity of the polysulfide polymer definedby the above formula can be altered by resort to a quantity other than23 for the constituent enclosed in the parentheses.

Specifically, in the constructed embodiment of the invention, BFCpoiysuliide sealant No. 44-169, a product f Better Finishes and CoatingsCompany lof Clifton, New Jersey, was used to form gasket 13. Thissynthetic rubber sealant is characterized by a tenacious adhesion toglass, metals, etc., and remains resilient throughout a temperaturerange from 60 F. to 23() F. The tube and safety plate bonded with thissealant was subjected to and successfully withstood an induced implosiontest of the type prescribed by the Underwriters Laboratories fortelevision cathode-ray tubes.

An adhesive gasket of the type herein considered can also be compoundedof other synthetic rubbers. For example, a .polyurethane -polymer curedwith a polyol such as polyester or polyether provides an excellentbonding sealant as does a silicon rubber base suitably cured by anoxidizing agent.

As will be shown the material constituting gasket 18 is applied as albead of paste by one of several methods to be described. Accordingly, aseries of small temporary spacers 19, see FEGURE 2, are first interposedbetween the faceplate and the safety Window and along their confrontingperipheral portions to maintain a minimum spacing between faceplate 13and safety plate 17 until the gasket material cures to a rubber-likeconsistency. Preferably, the spacers are constructed of a compliantmaterial such as felt, soft rubber, etc., and are aixed, .as by anadhesive, to either faceplace 13 or safety window 17 before the gasketmaterial is applied. Four spacers have been found sufficient forrectangular as well as round cathode-ray tubes. Moreover, so long ast-hey are of a yieldable material, the spacers need not be removed afterthe gasket material sets up since they have no adverse effect on thebonding ability of the gasket. On the other hand, and as will bedemonstrated, the requisite spacing can be secured without recourse tospacers by apparatus to lbe described. In any case, it is Ionlynecessary that the requisite spacing be maintained a time suflicient forthe bead of adhesive to cure since once the adhesive has cured, theresultant gasket constitutes the sole Imeans for securing safety window17 to the cathode-ray tube.

Referring now to FIGURE 3, there is illustrated an apparatus forpracticing one method of constructing a cathode-ray tube of the typeherein considered. As shown, tube 111 is supported face up in arotatable cradle 22 at a sealant dispensing station. lt should berecognized that this sealant dispensing station can be one of a seriesof stati-ons encountered by tube 10 during its manufacture and that thetube and cradle are transportable to other stations for such additionalprocessing as may be required as by a conveyor. Cradle 22 includes acollar 23 which is engaffeable with a drive pinion 24. A pressureoperated dispensing gun 25, connected to a supply of adhesive sealant,is pivotally supported adjacent tube 1S for displacement from thedepicted operative position to a storage position. The nozzle of gun 25is most advantageously fitted with a guillotine type shut-off valve inorderthat the iiow of the sealant can be instantaneously started orstopped. Thevalve itself is desirably controlled by a remotely actuatedsolenoid which is synchronized with drive pinion Z4.

Also located at the sealant dispensing station is a safety windowtransport 27 comprising a vertically displaceable hollow post 28 whichcommunicates, at one end, with a vacuum pump, not shown, and, at theother end, with a suction cup 29 which engages the outside surface ofsafety window 17. In this manner safety window 17 is releasablysupported over faceplate 13 and with its periphery in alignment with theperiphery of faceplate 13.

The processing steps entailed in bonding safety window 17 to tube 10with the apparatus of FIGURE 3 are instituted by inserting a tube incradle 22 at a prior station and Iattaching a safety plate havingpreviously affixed spacers 19 to suction cup 29. Alternatively, thespacers may be affixed to the periphery of faceplate 13. In any event,upon arriving at the sealant dispensing station, `drive pinion 24 ismechanically coupled to cradle collar 23 and gun 2.5 is pivoted from itsstorage position te the illustrated operative position in which theiiozzleis poised over the periphery of faceplate 13. Then,simultaneously, drive pinion 24 is actuated to rotate tube 10 at aconstant speed and the guillotine valve of gun 25 is opened.- -ii thisfashion 4a continuous uniform bead of adhesive' sealant is deposited onthe peripheral portion of faceplate 13, see FIGURE 3a. After onerevolution of tubel 10, drive pinion 24 is disengaged from collar 23,-the shut off valve for gun 25 is closed and the gun is swung out to thestorage position. The viscid nature of the sealant prevents it fromrunning down the side of the envelope, in fact its Visco-sity is suchthat it would not run or drip even if t-he envelope was inverted. Whenthe gun is clear of the faceplate, post 28 is lowered permitting safetyplate 17 to contact the bead 18 of sealant and spread the material uponthe confronting peripheral portions `of the safety plate and faceplate.If spacers 19 have previously been applied to the safety window or tothe faceplate, the vacuum holding force in cup 29 is releasedpermitting' safety window 17 to settle upon spacers 19 and bead 1S. Thetube and cradle are then transferred to a subsequent processing stationWhere curing of the sealant to a rubberlike consistency is acceleratedas by applying heat.

On the other hand, if spacers are not used, post 28 retains support ofWindow 17 when it contacts the bead of sealant 18 and maintains therequisite spacing 0f the window from the faceplate while heat is appliedto the bead to accelerate curing of the sealant. When the sealant curesto a resilient gasket of sufficient body to support the weight of window17, the window is released from cup 29.

It is further appreciated that means other than spacers 19 and post 28can be employed to maintain a desired spacing between windows 17 andfaceplate 13 until the polysulfide sealant cures.

An alternative construction for a bonded cathode-ray tube contemplates amodification of the bonding gasket to include a mounting guard orcushion for the tube. To this end, and as exemplified in FIGURES 4 and4a, such a gasket 35 comprises a principal bonding section 36 which isdisposed, as in the principal embodiment, between the confrontingperipheral portions of faceplate 13 and window 17 and a collar 37 whichsurrounds the frontal periphery of window 17. Collar 37 serves as aresilient mount for the tube in that it abuts the escutcheon or innerwall of the television cabinet when the tube is installed in a receiver.As an additional safe-guard, collar 37 preferably extends across theedge of safety plate 17 and down to crown 14 of the face plate. In thisfashion collar 37 protects the edge of window 17 during subsequenthandling of the tube.

As in the principal embodiment gasket 35 can be compounded of asynthetic rubber which is applied in paste form. Insofar as theprocessing ofthe alternate tube construction is concerned, at least twoapproaches are available. Window 17 can initially be bonded to.faceplate 13 by resort to the apparatus and technique detailed in thediscussion of FIGURE 3. Thereafter collar 37 is added simply by raisinggun 25 until it clears window 17 and then returning it to the operativeposition so that the nozzle of gun 25 is now poised over the rim of thesafety window. A second bead of paste is then deposited on the rim ofwindow 17 and crown 14 of the faceplate as tube rotates through onerevolution. Upon curing the two beads of sealant unite to form gasket35.

Alternatively, gasket 35 can be formed by the apparatus shown in FIGURE4 which, except for one detail, is the same as that of FIGURE 3. Theonly significant difference in the FIGURE 4 mechanism resides in the useof a multiple nozzle gun This gun extrudes two contiguous beads ofsealant thereby permitting gasket 3S to be formed by a single sealantdispensing operation.

In practicing the alternative method, prior to the sealant dispensingstep, a series of spacers 19 having previously deposited layers ofadhesive on each end are affixed about the periphery of faceplate 13.Window 17 is then aligned over face plate 13 and lowered onto thespacers. Upon making contact the adhesive on the exposed ends of thespacers secure the window in position for the next step. The tube isthus presented to the sealant dispensing station with window 17 alreadyin place. The tube drive pinion 24 and gun 25 are then actuated. Thelower nozzle of gun 25' discharges adhesive sealant at a pressuresufficient to force the sealant between the confronting peripheralportions of the safety window and faceplate a distance short of viewingarea 16 of the faceplate. Simultaneously, sealant is discharged from theother nozzle of gun 25 onto the rim of window 17 and the crown 14 of thefaceplate. As in the previously described gasket forming processes, thevalve of gun 25 is closed at the completion of one revolution of tube 10and the gun is returned to an inoperative or stand-by position. The tubeand cradle are then transported to a different station where the sealantis heat-cured to form` resilient gasket 35.

In each of the gasket forming processes thus far described, the adhesivesealant has been deposited upon the peripheral portion of a cathode-raytube face plate which is oriented face up. It is recognized, of course,that the positions of the tube and window can be inverted and that thesealant can be deposited upon the periphery of the safety window priorto lowering the tube upon the window. Moreover, because of the adhesionthe described sealants demonstrate for glass, neither the faceplate ofthe tube nor the safety window need be oriented in a horizontal plane.By the same token the constituency of the sealants is such that adeposited bead of sealant will cling to the receiving surface withoutrunning or dripping. Accordingly, in practicing the inventive processes,the orientations of the tube and safety window are immaterial. It isalso of no consequence whether the sealant is applied to the faceplateof the tube or to the periphery of the safety window. The end product isthe same in any case;

a cathode-ray tube having a safety window bonded thereto solely by aresilient gasket formed of a curable synthetic.

rubber base sealant.

The invention need not be limited to a tube employing an essentiallyflat safety window of the type shown in FIGURES 1-4 but alsocontemplates the alternate embodiment shown in FIGURE 5. This embodimentcornprises a tube 10 substantially identical to that shown in FIGURES1-4, in which like parts are identified by like but primed, referencenumerals. The safety plate 50 however comprises, in addition to aviewing panel 51, a fiange 52 which extends back from panel 51. The FIG-URE 5 construction may also employ spacers 19 to maintain the requiredminimum spacing between window 50 and faceplate 13. A gasket 53,comprising a cured bead of sealant, is interposed between theconfronting peripheral portions of safety plate 13 an-d viewing panel 51to bond window 50 to faceplate 13 and effect a hermetic sealtherebetween. By way of distinction, gasket 53 extends from theaforesaid peripheral portions back over crown 14 to the rim of flange52.

Gasket 50 is formed, preferably, by following the technique previouslydescribed in using the apparatus shown in FIGURE 3. An advantage of theFIGURE 5 embodiment resides in the development of a wider bondinggasket. This obtains by virtue of a spreading of the sealant as the faceplate and window are joined.

It is appreciated of course that a very significant percentage of thecathode-ray tubes employed in television receivers today are of therectangular type. Accordingly, while the foregoing teaching has relatedto round-faced picture tubes, it should be recognized that the inventionis equally applicable to rectangular picture tubes. Apparatus forapplying a bead of seaalnt to the periphery of a rectangular picturetube is rather complicated in comparison to that required for around-faced picture tube. For example, the sealant dispensing gun mustbe so controlled as to oscillate back and forth in order to follow theperiphery of a rectangular tube as the tube rotates. Additionally, thetube must be driven at a variable speed in order that the peripheralspeed of the tube, as it passes beneath the nozzle of the dispensinggun, remains constant. An oscillating path for the gun can be achievedby having it respond to a cam having a track which corresponds to theoutline of the rectangular tube being processed. Likewise, the speed ofthe cathode-ray tube can also be controlled by a drive cam having aprofile related to the outline of the rectangular tube. In this fashionthe peripheral speed of the rim of the tube passing beneath the gunremains constant thus assuring the disposition of a continuous uniformbead of sealant upon the periphery of the faceplate. Therefore in orderto avoid unduly complicating the drawings and specification discussionhas been limited to the round-faced tube.

It is further recognized that the cathode-ray tube itself can be bondedto a support frame or bezel with one of the adhesive sealants describedabove. In essence, such a support comprises a fian-ge having a dishedportion depending therefrom. The `dished portion is centrally ported orrelieved to permit -displafy of the viewing screen and has [overalldimensions greater than those of the tube faceplate. At selectedstations about its perimeter the fiange is aperture'd or :in some otherfashion provided with means which permit attaching the frame to anassociated chassis or cabinet.

The tube is united with the frame by nesting the frontal or display partof its envelope in the dished portion of the frame and then filling thespace between the envelope Wall and the frame with one of theaforementioned adhesives. Upon curing, the adhesive effects a permanentbond between the tube an-d the frame. Such an assembly achievessignificant economies in that straps and other hardware formerlyrequired to secure the tube to the chassis or cabinet are eliminated, asare attendant assembl-y costs.

While particular embodiments of the present invention have been shownand described, it is app-arent that changes and modifications may :bemade therein without dep-arting from the invent-ion in its `broaderaspects. The aim of the appended claims, therefore, is to cover all suchchanges and modifications as fall within the true spirit and scope ofthe invention.

I claim:

1. A cathode-ray tube comprising:

an envelope having a curved screen-bearing face plate with apredetermined viewing area;

a safety plate including a transparent section having overall dimensionsgreater than those of said viewing area and a .curvature conformingsubstantially to the curvature of said face plate;

and bonding means for securing said safety plate in an overlying spacedrelation to said face plate, said bonding means consisting of acontinuous layer of adhesive paste in intimate contact with and confinedto confronting portions of said envelope and said safety plate outsideof said face plate viewing area and cured to constitute a resilientgasket capable of yielda-bly accommodating displacement of said safetyplate relative to said face plate.

2. A cathode-ray tube comprising:

an envelope having a curved screen-bearing face plate with apredetermined viewing area;

a safety plate including a transparent section having overall dimensionsgreater than those of said viewing area and a curvature conformingsubstantially to the curvature of said face plate;

and bonding means for securing said safety plate in an overlying spacedrelation to said face plate and hermetioally sealing the spacetherebetween, said bonding means consisting of a continuous layer ofadhesive paste in intimate contact with and confined to confrontingportions of sai-d envelope and saidsafety plate outside of said faceplate viewin-g area and cured to constitute a resilient lgasket .capableof yieldably accommodating displacement of said safety plate relative tosaid face plate.

3. A `cathode-ray tube comprising:

an envelope having a curved screen-bearing face plate with apredetermined viewing area;

a safety plate including a transparent section having overall`dimensions greater than those o-f said viewing area and a curvatureconforming substantially to the curvature of said face plate;

bonding means for securing said safety plate in an overlying spacedrelation to said face plate and hermetically sealing the spacetherebetween, said bonding means consisting of a continuous layer ofadhesive -paste in intimate contact with confronting portions of saidenvelope and said safety plate outside of said face plate viewing areaand cured to constitute a resilient gasket capable of yieldablyaccommodating displacement of said safety plate relative to said faceplate;

and an edge guard for said face plate consisting of a bead of adhesivepaste disposed along the juncture of said envelope and said safety plateand extending onto the outer peripheral edge portion of said safetyplate a distance short of said face plate viewing area and cured to forma resilient cushion.

4. A cathode-ray tube comprising:

an envelope having a curved screen-bearing face plate with apredetermined viewing area;

a safety plate including a transparent section having overall4dimensions greater than those of said viewing area and a curvatureconforming substantially to the curvature of said face plate;

spacer means interposed between said face plate and said safety platefor establishing -a minimum spacing therebetween;

and 'bonding means for securing said safety plate in an overlying spacedrelation to said face plate and hermetically sealing the spacetherebetween, said. bonding means consisting of a continuous layer ofadhesive paste in intimate contact with and confined to confrontingportions of said envelope and said safety plate outside -of said faceplate viewing area and cured to constitute a resilient `gasket capableof yieldably accommodating displacement of said safety plate relative tosaid face plate.

5. A cathode-ray tube comprising:

an envelope having a curved screen-bearing face plate with apredetermined viewing area;

a safety plate comprising a transparent section having overalldimensions greater than those of said viewing area and a curvature.conforming substantially to the curvature of said face plate and adangle portion folded back from said transparent section;

and bonding means for securing said safety plate in overlying Aspacedrelation to said face plate and hermetically sealing the spacetherebetween, said bonding means consisting of a continuous layer :ofadhesive paste in intimate contact with and confined to confrontingportions of said envelope and said safety plate flange outside of saidface plate viewing area and curved to constitute a resilient gasketcapable of yieldably accommodating displacement of said safety platerelative to said face plate.

6. The method of assembling a cathode-ray tube having a curvedscreen-bearing face plate with `a predetermined viewing area and asafety plate having a transparent section with overall dimensionsgreater than those of the face plate viewing area and a -curvatureconforming substantially to the curvature thereof, which methodcomprises the following steps:

supporting said cathode-ray tube with its face plate disposed in apreselected plane;

applying a la-yer of adhesive paste to a selected peri-pheral portion of`at least one of said plates and only outside a yborder defined by saidface plate viewing area;

positioning said safety plate in an overlying relation with said faceplate and with the peripheral portions 'of said plates substantiallyaligned and in intimate contact with said adhesive;

and maintaining said safety plate and: face plate in a spaced relationand said peripheral portions -of said plates in contact with saidadhesive for a period of time sufcient to cure said adhesive and bondsaid safety plate to said cathode-ray tube.

7. The method of assembling a cathode-ray tube having a curvedscreen-bearing face plate with a predetermined viewing area and a safetyplate having a transparent section with overall dimensions greater thanthose of the face plate viewing area and a curvature conformingsubstantially to the curvature thereof; which method oomprises thefollowing steps:

supporting said cathode-ray tube with its face plate disposed in asubstantially horizontal plane;

applying a layer of adhesive paste to a selected peripheral portion ofsaid face plate and only outside the border defined by said face plateviewing area;

positioning said safety plate in an overlying relation to said faceplate and with the peripheral portions of said plates substantiallyaligned and in intimate contact with said adhesive;

and maintaining said safety plate and said face plate in a spacedrelation and said peripheral portions of said plates in Contact withsaid ladhesive for a period of time sutiicient to cure sai-d adhesiveand bond. said safety plate to said cathode-ray tube envelope.

8. The method of assembling a 4cathode-ray tube having a curvedscreen-bearing face plate with a predetermined viewing area and a safetyplate having a transparent section with 'overall dimensions :greaterthan those of the face plate viewing `area and a curvature conformingsubstantially to the curvature thereof, which method cornprises thefollowing steps:

supporting said cathode-ray tube with its face plate Idisposed in asubstantially horizontal plane and with said safety plate mounted uponand in a spaced aligned relation to said face plate; applying a layer ofadhesive paste to selected confronting peripheral portions of saidplates and only outside the border defined by said face plate viewingarea; and maintaining said safety plate and said face plate in a saidspaced relatio-n and said mripheral portions lof said plates in contactwith said adhesive for `a period of time sufficient to cure saidadhesive and bond said safety plate to said cathode-ray tube envelope.9. The method of assembling a cathode-ray tube having a curve-dscreen-bearing face plate with a predeter- :mined viewing area and asafety plate having a transparent section with overall `dimensionsgreater than those of the face plate viewing area and Ia curvatureconforming substantially to the curvature theenof, vwhich methodcomprises the following steps:

supporting said cathode-ray tube with its face plate dsiposed in apreselected plane; applying |a rst layer of adhesive paste to a selectedperipheral portion of said face plate outside .a lborder defined -bysaid face plate viewing area; positioning said safety plate in anoverlying relation to said face plate and with the peripheral portionsof said plates substantially aligned and in intimate conytact with saidadhesive;

applying a second layer of adhesive paste along the periphery of saidsafety plate and extending onto .said safety plate a distance short ofsaid face plate viewing area;

and maintaining said safety plate and said face plate in a spacedrelation and said peripheral portions of said plates in contact withsaid first layer of adhesive for a period of time suflicient to curesaid first lalyer to bond said safety plate to said cathode-ray tubeenvelope and to cure said second layer t-o pnovide a resilientperipheral cushion for said safety plate.

References Cited by the Examiner UNITED STATES PATENTS 2,293,529 8/ 1942Bedford l78-7.82 X 3,113,347 12/196-3 Kufrovich 220-2.1 X 3,130,8544/1964 Casciari 220-2.1

FOREIGN PATENTS 904,616 8/ 1962 Great Brit-ain.

THERON E, CONDON, Primary Examiner. MARTHA L. RICE, Examiner.

1. A CATHODE-RAY TUBE COMPRISING: AN ENVELOPE HAVING A CURVEDSCREEN-BEARING FACE PLATE WITH A PREDETERMINED VIEWING AREA; A SAFETYPLATE INCLUDING A TRANSPARENT SECTION HAVING OVERALL DIMENSIONS GREATERTHAN THOSE OF SAID VIEWING AREA AND A CURVATURE CONFORMING SUBSTANTIALLYTO THE CURVATURE OF SAID FACE PLATE; AND BONDING MEANS FOR SECURING SAIDSAFETY PLATE IN AN OVERLYING SPACED RELATION TO SAID FACE PLATE, SAIDBONDING MEANS CONSISTING OF A CONTINUOUS LAYER OF ADHESIVE PASTE ININTIMATE CONTACT WITH AND CONFINED TO CONFRONTING PORTIONS OF SAIDENVELOPE AND SAID SAFETY PLATE OUTSIDE OF SAID FACE PLATE VIEWING AREAAND CURED TO CONSTITUTE A RESILIENT GASKET CAPABLE OF YIELDABLYACCOMMODATING DISPLACEMENT OF SAID SAFETY PLATE RELATIVE TO SAID FACEPLATE.